1. Field of the Invention
The present invention relates to movable body drive systems and movable body drive methods, pattern formation apparatuses and methods, exposure apparatuses and methods, device manufacturing methods, and decision-making methods, and more particularly to a movable body drive system and a movable body drive method that drive a movable body along a predetermined plane, a pattern formation apparatus equipped with the movable body drive system and a pattern formation method using the movable body drive method, an exposure apparatus equipped with the movable body drive system and an exposure method using the movable body drive method, a device manufacturing method using the pattern formation method, and a decision-making method in which correction information of measurement values of an encoder system that measures position information of a movable body in a predetermined direction is decided.
2. Description of the Background Art
Conventionally, in a lithography process in the manufacturing of microdevices (electron devices) such as semiconductor devices and liquid crystal display devices, exposure apparatuses such as a reduction projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a reduction projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are relatively frequently used.
In these types of exposure apparatuses, in order to transfer a pattern of a reticle (or mask) to a plurality of shot areas on a wafer, a wafer stage that holds the wafer is driven in XY two-dimensional directions by, for example, a linear motor or the like. In particular, in the case of the scanning stepper, not only the wafer stage but also a reticle stage is driven by a linear motor or the like in a scanning direction in a predetermined stroke. Generally, position measurement of the reticle stage or the wafer stage is performed using a laser interferometer whose measurement values have stability for a long period and which has a high resolution.
However, more accurate position control performance has been required due to finer patterns to cope with higher integration of semiconductors, and recently the short-term fluctuation of the measurement values caused by variation in the temperature of the atmosphere on the beam optical path of the laser interferometer has been accounting for a large share of the overlay budget.
Meanwhile, as an apparatus other than the laser interferometer to be used for position measurement of a stage, an encoder can be cited, but because the encoder uses scales and the scales lack mechanical long-term stability (due to drift of scale pitch, fixed position drift, thermal expansion, and the like), and therefore, the encoder suffers from the disadvantages of lacking the linearity of the measurement values and being inferior in the long-term stability, compared with the laser interferometer.
In view of the disadvantages of the laser interferometer and the encoder as described above, various types of apparatuses that measure the position of a stage using both a laser interferometer and a position detection sensor (encoder) that uses a diffraction grating have been proposed (refer to Kokai (Japanese Unexamined Patent Application Publications) No. 2002-151405 and No. 2004-101362, and the like.)
Further, although a measurement resolution of a conventional encoder was inferior to that of an interferometer, recently encoders having the measurement resolution equal or superior to the laser interferometers have come out (e.g. refer to Kokai (Japanese Unexamined Patent Application Publication) No. 2005-308592 and the like), and the technique of combining the laser interferometer and the encoder has been gathering attention.
However, for example, in the case the encoder is used for position measurement of a wafer stage within a moving plane in an exposure apparatus, even when the position of a stage on which a scale (grating) is arranged is measured using one encoder head, if the relative motion between the head and the scale occurs in a direction other than a direction to be measured (measurement direction), the variation in the measurement value (count) is detected and a measurement error occurs in most cases. In addition, in the case the encoder is actually applied to a wafer stage of an exposure apparatus, because a plurality of encoder heads need to be used for one scale, there is also the inconvenience that an error occurs in a count value of the encoder due to, for example, the difference in gradient (tilt of the optical axis) between the encoder heads, and the like.